Fringe field switching mode liquid crystal display

ABSTRACT

Disclosed is a fringe field switching mode liquid crystal display. The fringe field switching mode liquid crystal display of the present invention comprises a transparent insulating substrate; a plurality of gate bus line arranged in selected direction on the transparent insulating substrate, the gate bus line is arranged so that each element of the pair separated at a first distance is arranged a plurality of pairs at a second distance wider than a first distance; a plurality of common bus lines arranged on the centers of each gate bus line separated at the second distance, being in parallel with the gate bus line; a plurality of data bus lines arranged crossing with the gate bus line and common bus line to define a unit pixel; a thin film transistor disposed at the intersection of the gate bus line and data bus line; a counter electrode disposed in a unit pixel area and made of a transparent conductor, being in contact with the common bus line; and a pixel electrode overlapping with the counter electrode in the unit pixel and made of a transparent conductor, being in contact with the thin film transistor.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a fringe field switching modeliquid crystal display, and more particularly a fringe field drivingliquid crystal display in which the structure is transformed to preventshorts between a gate bus line and a common bus line.

[0003] 2. Description of the Related Art

[0004] A thin film transistor liquid crystal display (hereinafterreferred as TFT-LCD) generally has advantages of light weight, thinthickness and low power consumption. Therefore, it has been substitutedfor Cathode-ray tube (CRT) in a terminal of information apparatus and avideo unit, and recently, it is widely used in a notebook PC and monitormarket.

[0005] The TFT-LCD comprises an array substrate and a color filter,which are combined with a liquid crystal layer interposed between them.The array substrate has a structure that TFTs are disposed in each pixelarranged in a matrix type and the color filter substrate has a structurethat a red, a green and a blue color filters are arranged correspondingto each pixel.

[0006] The TFT-LCD has been adopted TN (Twist Nematic) mode as a drivingmode, however, the TN mode LCD has a disadvantage of narrow viewingangle. Accordingly, in order to solve the problem, an In-Plain Switching(hereinafter referred as IPS) mode has been proposed.

[0007] The IPS mode LCD has a wide viewing angle, however, it hasdisadvantages of a low aperture ratio and a low transmittance since acounter electrode and a pixel electrode are made of opaque metals. Afringe field switching (hereinafter referred as FFS) mode LCD has beenproposed in order to improve the aperture ratio and transmittance of theIPS mode LCD.

[0008] In the FFS mode LCD, the counter electrode and the pixelelectrode are made of transparent conductors and are designed which thedistance between electrodes is narrower than that between substrates.And liquid crystals having negative dielectric anisotropy are used inthe FFS mode LCD. Accordingly, a fringe field is formed between theelectrodes and the liquid crystals on the electrodes are also driven bythe fringe field, thereby realizing high brightness as well as wideviewing angle.

[0009]FIG. 1 shows an array substrate of a conventional FFS mode LCD. Asshown in FIG. 1, a gate bus line (2) and a data bus line (6) arecross-arranged, thereby defining a unit pixel area. A TFT (10) isarranged as a switching device near the intersection of the gate busline (2) and the data bus line (6). The TFT (10) comprises a gateelectrode that is a part of the gate bus line, a semiconductor layer (3)on the gate electrode, a drain electrode (6 b) overlapping with one sideof the semiconductor layer (3), being protrude from the data bus line(6), and a source electrode (6 a) overlapping with the other side of thesemiconductor layer (3).

[0010] A counter electrode (5) is disposed in a unit pixel area. Thecounter electrode (5) made of a transparent conductor and has a plateshape. A part of the counter electrode (5) is electrically in contactwith a common bus line (4), thereby continuously applying common signalsfrom the common bus line (4).

[0011] The common bus line (4) comprises a first part (4 a) disposed inparallel with the gate bus line (2), being electrically in contact withthe counter electrode (5) and a second part (4 b) which is extended fromthe first part (4 a) to be in parallel with the data bus line (6) in aunit pixel, being in contact with both edges of the counter electrode(5) to be a shading means.

[0012] A pixel electrode (7) is disposed in a unit pixel to overlap withthe counter electrode (5). The pixel electrode (7) made of a transparentconductor and is formed in a slit shape comprising a plurality of slitsdisposed in parallel with the data bus line (6). The pixel electrode (7)is insulated with the counter electrode (5) by a gate insulating film(not illustrated) and is electrically in contact with a source electrode(6 a) of TFT (10).

[0013] However, conventional FFS mode LCD has a narrow distance (L1)between a gate bus line and a common bus line, thereby increasinggeneration probability of shorts between them. As a result, the qualityof product is degraded. That is, when a short is generated between thelines, a high voltage loaded on the gate bus line is loaded on thecommon bus line. Accordingly, the high voltage may cause the common busline to be defective, thereby deteriorating the product quality.

SUMMARY OF THE INVENTION

[0014] Therefore, an object of the present invention is to provide a FFSmode LCD preventing the generation of shorts between a gate bus line anda common bus line.

[0015] And, another object of the present invention is to provide a FFSmode LCD preventing degradation of products due to a short between thelines.

[0016] In order to achieve the above objects, the FFS mode LCD accordingto the present invention comprises: a transparent insulating substrate;a plurality of gate bus line arranged in selected direction on thetransparent insulating substrate, the gate bus line is arranged so thateach element of the pair separated at a first distance is arranged aplurality of pairs at a second distance wider than a first distance; aplurality of common bus lines arranged on the centers of each gate busline separated at the second distance, being in parallel with the gatebus line; a plurality of data bus lines arranged crossing with the gatebus line and common bus line to define a unit pixel; a thin filmtransistor disposed at the intersection of the gate bus line and databus line; a counter electrode disposed in a unit pixel area and made ofa transparent conductor, being in contact with the common bus line; anda pixel electrode overlapping with the counter electrode in the unitpixel and made of a transparent conductor, being in contact with thethin film transistor.

[0017] The counter electrode may be disposed in each unit pixel area orone counter electrode of a body type may be disposed in two unit pixelareas defined by a gate bus line.

[0018] The common bus line may be formed in a line type or it maycomprise a first part of a line type and a second part. The first partis disposed in parallel with the gate bus line, being in contact with apart of the counter electrode and the second part is protruded from thefirst part in a unit pixel, disposed in parallel with the data bus line,being in contact with both edges of the counter electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above objects, and other features and advantages of thepresent invention will become more apparent after a reading of thefollowing detailed description when taken in conjunction with thereferenced drawings.

[0020]FIG. 1 shows an array substrate of conventional FFS mode LCD.

[0021]FIG. 2 shows an array substrate of FFS mode LCD according to apreferred embodiment of the present invention.

[0022]FIGS. 3 and 4 show a counter electrode and a common bus line ofFFS mode LCD according to another preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0023]FIG. 2 shows an array substrate of FFS mode LCD according to apreferred embodiment of the present invention.

[0024] Referring to FIG. 2, a plurality of gate bus lines (12) arearranged in a line on a transparent insulating substrate (notillustrated). The gate bus lines (12) are arranged so that each elementof the pair separated at a first distance is arranged a plurality ofpairs at a second distance wider than a first distance. Common bus lines(14) are arranged in parallel with the gate bus line (12) on the centersof each gate bus line (12) separated at a second distance. A pluralityof data bus lines (16) are arranged crossing with the gate bus line (12)and the common bus line (14), thereby defining a unit pixel.

[0025] Herein, the unit pixel is defined by one gate bus line (12), onecommon bus line (14), and a pair of data bus lines (16). Therefore, thesecond distance between the gate bus lines corresponds to the size oftwo unit pixels and the common bus line (14) is disposed to define thesize of each unit pixel.

[0026] A TFT (20) is then disposed as a switching device near theintersection of the gate bus line (12) and the data bus line (16). TheTFT (20) comprises a gate electrode that is a part of the gate bus line(12), a semiconductor layer (13) disposed on the gate electrode, a drainelectrode (16 b) which is protruded from the data bus line (16) tooverlap with one side of the semiconductor layer (13), and a sourcedrain electrode (16 a) overlapping with the other side of thesemiconductor layer (13).

[0027] A counter electrode (15) is disposed in each unit pixel. Thecounter electrode (15) is made of a transparent conductor in a platetype. And, counter electrodes are in contact with one common bus line(14) even when the counter electrodes are disposed in two unit pixelsdefined by the gate bus lines (12) separated at the second distance.

[0028] A pixel electrode (17) is disposed in the unit pixel to overlapwith the counter electrode (15). The pixel electrode (17) is made of atransparent conductor in a slit type. And, the electrode (17) isinsulated with the counter electrode (15) by a gate insulating film (notillustrated), being in contact with a source electrode (16 a) of the TFT(20).

[0029] In the array substrate of the FFS mode LCD according to thepresent invention as described above, a distance (L2) between a gate busline (12) and a common bus line (14) is wider when compared to theconventional distance (L1), thereby remarkably decreasing the generationprobability of shorts between the lines.

[0030] While the gate bus lines (12) to be dispose at the first distancemay cause a short between them. But since one common bus line (14) isdisposed in two unit pixels unlike a conventional structure that onecommon bus line is disposed in one unit pixel, the distance between gatebus lines (12) may be increased. As a result, the distance between thegate bus lines (12) is increased, thereby preventing the short betweenthe gate bus lines (12).

[0031] Consequently, according to a FFS mode LCD of the presentinvention, a short between a common bus line and a gate bus line may beprevented by optimizing the structure thereof, thereby improving aquality of common bus line and preventing deterioration of products.

[0032]FIGS. 3 and 4 show a counter electrode and common bus line of FFSmode LCD according to another embodiment of the present invention.

[0033] Referring to FIGS. 3 and 4, a common bus line (14) is formed in aH-shape in two adjacent unit pixels. That is, the common bus line (14)comprises a first part (14 a) of a line type which is disposed inparallel with a gate bus line (12) to define a unit pixel and a secondpart (14 b) which is protruded from the first part (14 a) and isdisposed in parallel with a data bus line (16), overlapping with bothedges of the counter electrode to be a shading means.

[0034] The counter electrode (15) is formed in a plate-shape and may bedisposed in each unit pixel as shown in FIG. 3 or disposed in a bodytype in two unit pixels defined by the gate bus lines (12). When thecounter electrode (15) is disposed in a body type in two unit pixels, anetching margin to a transparent conductor is increased and the contactresistance is decreased by enlarging the contact area with the commonbus line (14).

[0035] As described above, according to the present invention, thestructure of a gate bus line and a common bus line is transformed toprevent generation of defects due to a short between the lines, therebyimproving the yield.

[0036] While this invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made to the described embodiments without departing from the spiritand scope of the invention as defined by the appended claims.

What is claimed is:
 1. A fringe field switching mode liquid crystal display comprising: a transparent insulating substrate; a plurality of gate bus line arranged in selected direction on the transparent insulating substrate, the gate bus line is arranged so that each element of the pair separated at a first distance is arranged a plurality of pairs at a second distance wider than a first distance; a plurality of common bus lines arranged on the centers of each gate bus line separated at the second distance, being in parallel with the gate bus line; a plurality of data bus lines arranged crossing with the gate bus line and common bus line to define a unit pixel; a thin film transistor disposed at the intersection of the gate bus line and data bus line; a counter electrode disposed in a unit pixel area and made of a transparent conductor, being in contact with the common bus line; and a pixel electrode overlapping with the counter electrode in the unit pixel and made of a transparent conductor, being in contact with the thin film transistor.
 2. The fringe field switching mode liquid crystal display according to claim 1 , wherein the common bus line comprises a first part of line type disposed in parallel with the gate bus line, being in contact with a part of the counter electrode and a second part protruded from the first part in a unit pixel and disposed in parallel with the data bus line, being in contact with both edges of the counter electrode.
 3. The fringe field switching mode liquid crystal display according to claim 1 , wherein the counter electrode is formed in a plate shape.
 4. The fringe field switching mode liquid crystal display according to claim 1 , wherein the counter electrodes are disposed in each unit pixel area.
 5. The fringe field switching mode liquid crystal display according to claim 4 , wherein the counter electrodes disposed on the upper and lower parts of the common bus line are all in contact with the common bus line.
 6. The fringe field switching mode liquid crystal display according to claim 1 , wherein the counter electrode is disposed in a body type in two unit pixel areas between gate bus lines separated at the second distance.
 7. The fringe field switching mode liquid crystal display according to claim 1 , wherein the pixel electrode is formed in a slit shape. 